Control of shape and size of nanopillar assembly by adhesion-mediated elastocapillary interaction
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Abstract
Control of self-organization of nanofibers into regular clusters upon evaporation-induced assembly
is receiving increasing attention due to the potential importance of this process in a range of applications including
particle trapping, adhesives, and structural color. Here we present a comprehensive study of this phenomenon
using a periodic array of polymeric nanopillars with tunable parameters as a model system to study how geometry,
mechanical properties, as well as surface properties influence capillary-induced self-organization. In particular,
we show that varying the parameters of the building blocks of self-assembly provides us with a simple means of
controlling the size, chirality, and anisotropy of complex structures. We observe that chiral assemblies can be
generated within a narrow window for each parameter even in the absence of chiral building blocks or a chiral
environment. Furthermore, introducing anisotropy in the building blocks provides a way to control both the
chirality and the size of the assembly. While capillary-induced self-assembly has been studied and modeled as a
quasi-static process involving the competition between only capillary and elastic forces, our results unequivocally
show that both adhesion and kinetics are equally important in determining the final assembly. Our findings
provide insight into how multiple parameters work together in capillary-induced self-assembly and provide us
with a diverse set of options for fabricating a variety of nanostructures by self-assembly.